Continuous furnace and process of regulating atmospheric conditions in furnaces.



C. P. WOOD.

CONT'NUOUS FURNACE AND PROCESS FOR HEGULATING ATMOSPHERC CONDITIONS INFUHNACES.

APPLICATION FILED SEPT. 19. 1917.

1,297,629. Pdtend Mm. 1s, 19m.

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COO/029 Zone C. P. WOOD.

CONTINUOUS FURNACE AND PROCESS FOR REGULATING ATMOSPHERIC CONDITIONS INFURNACES.

APPLICATION FILED SEPT. I9. I9I1.

1,297,629. Patented Mar. 18, 1919.

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CHARLES-r; woon, or NEW YORK, N. Y;

CONTINUOUS FURNAUE AND Pnocnss or.NEGULATINGATMOSPHERIC-coNDi'rroNs 1NvisiUaNacEs.

Application filed September 19, 1917.4 Serial No. 192,081.

' the tunnel type, have a pre-heating-zone,

a combustion zone and a cooling zone,

through which the material is successively passed by mechanical means,while undergoing treatment. lSuch furnaces effect a great savinginlabor, time and fuel, cost of operation, repairs, maintenance andinterest on capital invested, because the process involved in theiroperati-on and the treatment of the material is continuous, orsemicontinuous. l v

Theobject. ofthe present invention 1s to provide an improved furnace and-a process which will regulate the character of the atmosphere in thatportion of a' continuous furnace in which cooling occurs; for instance,in the cooling zone of .a tunnel furnace.'

The proce'ssis adapted for usein various metallurgical operations, andthe heat treatf ment of glassware and other materials. VVhileI expresslydisclaim any intention to limit the application of the process, it isshown and described as used for'the bright annealing of steel sheets, towhich it'is particularl applicable.

AIn t e anneali of steel particularly -steel sheets, it hasnee n founddesirable to allow the steel tocool in alreducing atmosphere to preventoxidation which causes discoloration and hard4 spotsV in the sheets.Heretofore the various methods which have been adopted with a view tosecuring this result, have generally been expensive and unsatisfactoryin that they have requiredincreased labor and fuel consumption.

In my furnace and process, while the materialis passing through thecooling zone, itv

is envelopedin an atmosphere consisting entirely of unburned gas whosecirculation is regulated in such a manner that the air requisite forcombustion of thisV gas is supplied in the general region where it isintended combustion ofthe gas shall occur, means being provided toprevent access of air to the cooling zone and thereby to insure againstdilution of the gaseous prism which is designed to completely immersethe material being cooled. The products of combustion are taken olf inany suitable manner andgive up their heat to incoming material While enroute to their point of escape.

My furnace and process contemplates the regulation of atmosphericconditions in the cooling zone where the unburned raw gas exists,because, afterscombustion occurs the character of the atmosphere is notsubject to the nicely regulated adjustment possible prior to combustion,certainV temperature changes and chemical actions involved in combustionpreventing such regulation. It is possible, however, to regulateatmospheric conditions to some extenteven after combustion has occurredby effecting the desired mixture of gases before combustion occurs andthis mixture may also be highly preheated before the air or oxygenrequired for combustion is allowed to mix with the 'com b stible gas.

l y process 1s a continuous one as it contemplates the maintenance ofthe point of burning oil of the end of the gas column or prism 1n thesame general region by preventin the admission of air, except asregulated 1n the process itself, into the cooling zone occupied by thegas column when carsI bea-ring the material being treated are ad--mitted to, and removed from, the furnace.

This exclusion of air when a car is admitted to, or removed from, thetunnel, prevents the sneaking back of outerv airinto the gas within thecooling zone, and it also prevents explosions.l

When carrying out the process in a continuous furnace, for instance, oneof the tunnel type, the cooling zone of the tunnel can be filled withunburned gas, supplied andregulated at will by suitable means.

Patented Mar. 184, 1919..

Provision is made to prevent accessI of air to the cooling Zone and,consequently, the unburned gas will always drift in the direction of theStack, due to impulse supplied by the draft. As the column or prism ofgas reaches the combustion zone, air is fed thereto under any desiredregulation to meet requirements for combustion and it is then ignited,as, for insta-nce, by a pilot burner. Since -the general direction ofthe draft is toward the stack and because additional raw gas iscontinuously supplied, under any desired regu-latiomto the column orprism of gas in the cooling zone an access of airv to Fthe cooling zoneis provided, the air supplied to the gas in the general region of thepoint of combustion will not circulate backward or penetrate the gascolumn in the cooling zone; consequently, combustion Will occur only asthe column of gas advances to the point. or general region Where air isadmitted to the furnace. The result is Ithat the process involves theburning off of the end of -a continuously drifting or advancing gasco'lumn at a maintained or relatively fixed region or point; other gasbeing continuously supplied back of this point or region to-maintain agas prism of substantially constant proportions. Not only does thisprocess supply hea-t producing means for operating the furnace but itmaintains a reducing atmosphere in the cooling zone in which thematerial, steel sheets for instance, is enveloped While undergoingcooling.

:The process a-lso contemplates the utilization, if desired, of theadditional step of special admission of gas at the delivery point of thefurnace, to regulate conditions lthere should it be 'found necessary ordesirable.

Air locks at the admission and exit pomts of the furnace afford themeans for preventing explosions and for' preventing adaol 5 -in carryingoutthe process.

The present process is applicable to some furnaces intended foroperation lfor other purposes but which are not 4applicable at presentto certain' metallurgical or heat treatment'y operations because 0f thefact that oxidation or carbonization or other actions would occurtherein after the material 'had' been brought up to the Ipoint ofmaximum temperature. The furnace which is disclosed herein to illustratethe process, While'embodying improvements, is an p illustrativedisclosureonly, V'in so far as the process iis concerned as othercontinuousor semi-continuous, furmici-'Ls'l may be used; .nor does theprocess depend upon any particular mechanical features of the furnace inwhich it is carried out. In the furnace disclosed a sand seal is shownfor separating the hot upper 'sections of the furnace from the coollower section .in which travels the mechanical means for conveying thematerial 0r ware; other methods or means-may be employed for making thisdivision of upper and lower sec-tions effective.

In the accompanying drawings- Figure 1 is a side elevation of a furnacechamber used in carrying out my process;

Fig. 2 is a plan view thereof;

Fig. 3 is a longitudinal section; and

Fig. 4- is a cross section on line 4-4, Fig. 2.

The furnace comprises a. tunnel 1 having a prcheating zone 2, acombustion zone 3, and a cooling zone -L The cooling zone -t has ports,Fig. 3, to which fuel gas is supplied through ducts 5 which havesuitable valves-or dalnpcrs s0 that lthe supply of gas to the differentpoints of the length of the cooling zone may be regulated as desired.The exact location of 'the gas ports to which ducts 5 lead will varywith the purpose for which the furnace is to be used, but they willalways be arranged t0 deliver the gas within ythe cooling Zonel 4. Theproducts of combustion are taken out of the tunnel through the opening 7into the stack 6.

Any suitable damper or dampers 6 may be employed to regulate the draftthrough the :tunnel and into the stack 6.

Air is admitted through ports 11 in the combustion zone 3.

At 'the inlet of the furnace there is an air lock 8 and at Ithe outletthere are air locks 9 and 10. The air lock 8 has doors 17 and 18. Thedoors 17, 18 may be operated from the exterior of the furnace by anysuitable means, 17, 18, but the door 18 need not necessarily be operatedfrom the outside because conditions in the air lock 8 are such that theoperator can remain inside the lock after closing the door 17. When thedoor 18 is opened, the car which carries the material on Ware tobetreated may be pushedin'to the active length of the. tunnel by atransmission 19 of any suitable kind; the one shown consisting ofsprockets and a chain with any convenient form of dog for engaging aportion of the car for pushing or -pulling the car When the chain isoperated. Succeeding cars push other cars,

ahead of them, but othermeans for conveying the material may be employed.Without. affecting the process.

The air locks 9 and 10 are providednwith doors 14, 15, 16, .which can beopened from -the outside Without admitting air to the locksl Anysuit-able means such as shown at 14, 15, 16a may be employed for thispurpose.

Atransmission 20, operable from the exengage a yportion of the car sothat the transmission picks up the car from the end ofthe train withinthe furnace, moving it more" rapidly than the other cars and taking itinto the air lock 9 when thedoor 14 is opened. The door 14 is thenclosed behind the selected car and door 15' opened and the car movedinto the air lock 10 by the continued operation of transmission 20. Thedoor 15 is then closed and the car may be taken out into the atmosphereon opening the door 16. By the yuse .of twoair locks, the cooling zone 4is prevented from being placed in direct communication with the outsideatmosphere and any inrush-of air is thus prevented.

The air locks prevent admission of air into the cooling zone and body ofgas therein contained, when a car is admitted te the tunnel. Explosionsare thereby prevented; and, further, by thus preventing commingling ofouter air with the gas in the gas zone, the point of combustion ismaintained at the end lot the gas column -in substantially the sameregion at all times, thus preventing the air from sneaking back into thegas' zone and negativing the very effect (immersion of the material in abody of gas) which is the object of the invention. My process is acontinuous one, as the point of burning oil' of the end of the gascolumn is maintained* at all times regardless of admission of the carsto, and their removal from, the furnace.

Since a certain amount of space is required to provide perfectcombustion and to insure freedom of draft throughout the combustion zone,3 and the preheating zone 2, these sections of the furnace may be widerthan the cooling zone 4 in ,which the volume of gas should be kept assmall as possible. The line A, Fig. 4, indicates,I the greater width ofthe pre-heatingy zone 2, while the line B indicates the lesser Widthof-the cooling zone 4. This difference in size renders it possible toreduce the volume of gas maintained in the cooling zone 4 withoutaffecting the char- .acter of the atmosphere and its regulation in thesaid zone. In afurnace of the character disclosed, the cars have aheat-resisting deck 24 which forms a division between the heated uppersection of the furnace andthe lower section 'which contains,v themech-ani- .and the consequent 'transfer of heat from the cally. movingparts which shouldbekept at a lower temperature in orderfte,l

shown a sand seal 25 'to prevent circulation upper to the lower section,but other means can be :used witl 1out any change in the prin# clple vof mamtalnlng a or an adjustable and regulablequantity of gas or gasesin the cooling zone' 4;

Operation: As theconveying means travels along the pre-heating zone 2and approaches `the furnace or combustion zone 3, the ware or materialcarried thereby is gradually heaty#ed by absorbing heat from theproducts of combustion. The heat to -be maintained is regulated byregulation of the amount of gas admitted into the cooling zone 4 throughthe d ucts 5 and the amount of air admitted through the air ports 11.Having passed the combustion zone, the cars enter. the cooling zone 4which is completely filled With raw or unburned gas. The cooling zone isof-such a length and so proportioned that the material under treatmenttherein has cooled down to the required temperature by the time the Wareor material reaches the door 14. y i t If desirable in certainoperations, the lock 9 may be filled with as admitted through a portfrom a suitab y controlled duct 22, while the conveyer is moving fromthe cooling zone 4 -into the lock 9. The door 14 would then be closedand, if necessary or desirable, the gas could be taken out through adraft port 23. Resortneed not be had to this step. but I refer to thisfeature to show the Hexibility of operation under the proc-l ess to takecare of the most extremerequirements for maintaining a reducingatmosphere in the cooling zone of the furnace.

To insure against admission of air to the cooling zone I may provide anysuitably controlled draft means 13 which may be either a stack or afanor a combination of the two, adjustable by any Well known means andcarefully set by draft gages so that in case the discharge end of thefurnace should have to be opened to the atmosphere, the draft would 'beso balanced lthat there would be no inrush of air to the cooling zone 4.

Tlieeooling zone 4 being filled with unburned or raw gas, the draftcauses the column or prism -of gas to drift toward the prcheating zone2.and as the prism4 of gas rea-ches the fcombustion zone 3, it receivesthrough the ports 11 the necessary air for combustion. Ignition may bestarted and maintained by 4pilot burners 12. Since the y vzone, that is,in the regionl where the .air is admltted through the ports 11.

The process contemplates, therefore, the continuous ad- "vanceof a prismof gas whose end 'is burned off as it reaches a given'point, additionalgas being supplied back of' this point to'maintain a* gaav prism ofconstant lpro rtions. Aftery the point 4of maximum'heat as been reachedin the combustion zone, the ware or material is immediately enveloped inthe raw or unburned gas in the cooling zone 4. In the treatment of steelsheets, for instance, there is obtained in the cooling zone a reducingatmosphere which prevents. oxidation and consequent discoloration andhard spots. Any other material may be treated by the process.

I do not limit the process to the use of a reducing atmosphere nor tothe supply -of gas only .to the cooling zone 4; air may be admittedthrough some of the ducts 5,01 several gases maybe introduced into thecooling zone and the proportions adjusted until the desired atmosphereis maintained in the furnace.

VVh'at I claim is:

l. A process for regulating atmospheric conditions in furnaces,consisting in v'maintaining and advancing a gaseous body or column, andburning ofi' the advance portion of said body or column as said body orcolumn progresses toa region Where combustion is desired, Whilepreventingaccess of air to the gaseous body or column other than such asrequired for combustion,- thereby maintaining a relatively fixed ormaintained point of combustion of said gaseous column or body. v

2. A process for regulatinggatmospheric conditions in continu-ous orsemi-continuous` furnaces, consisting in maintaining .a cooling zonecomprlsmg a substantially constant,

ycontinuously fed and continuously advancing gaseous body or column,maintammg a substantially fixed region of combustion by supplying air tothe advance portion of said gaseous body orcolumn and burning ofi' saidadvance portion in the general region of the air supply as fast as saidbody or column advances and preventing access of air to the gaseous bodyor column when the furnace is opened to admitl or discharge the materialabout to be, or which has been, treated.

3. A process for regulating atmospheric conditions in furnacesconsisting in continuously advancing a gaseous body or column to a givencombustion region of the furnace, continuously supplying air to, 'andburning off the advance portion of, said gaseous body or column as itreaches Said combustion reion, continuously replenishing the gaseouslody back of said combustion region as fast.

' as the advance portion of the body is burned tively fixed ormaintained point of combustion.

tinuo-us or. semi-continuous furnaces, consisting'in irstpassing thematerial through a relatively fixed or constantl combustion zonemaintained at the advance portion of a body or column of unburned gasesthe constituents of which are regulable both as to quantity andtemperature, then through the unburned'gases to effect cooling of thematerial while ,immersed therein, and, finally, out of 4. A process fortreating material in conthe body of unburned gases.. while preventmgaccess of air to the gaseous body.

5. A furnace provided with a combustion zone, a cooling zone, means foradmitting gas to the cooling zone and for maintaining it there as agaseous body or prism, means for supporting combustion of the advanceend of' the gaseous body in the combustion zone, and means forpreventing access of air to the furnace when it is opened to admit ordischarge the material about to be, or Which has been, treated, therebypreventing access of air to the' gaseous body in the cooling zone.

6. A furnace provided With a combustion zone, -a cooling zone, means foradmitting gas to the'eooling zone and for maintaining it there as agaseous body or prism, means for supporting combustion of the advanceend of the gaseous body in the combustion zone, and air locks at theentry and exit parts of the furnace which prevent access of air when thefurnace is opened to admit or discharge the material about to be, orWhich has been, treated, thereby preventing access of lair to,thegaseous body in the cooling zone.

7. Aif'urnace p-rovided with a combustion vthe furnace which preventaccess of air when the furnace isopened to admit or 1discharge thematerial aboutl to be, or which has been, treated, thereby preventingaccess of air to thev gaseous body in the cooling zone, and meansv foreffecting any desired gaseous condition in the air lock at the exitportion-of the furnace to re late conditions therein.

In testimony rvlliereof I hereunto aiiix my signature.

CHARLES P. WOOD.

